An innovative, software-defined OFDM (orthogonal frequency division multiplexing) back-channel communication for ultra-low power (ULP) Internet-of-things (IoT) devices is disclosed. This technique enables interconnecting heterogeneous ULP IoT devices through an OFDM based back-channel that can be realized with existing WiFi (IEEE 802.11a/g/n) infrastructure without any hardware modification. The OFDM back-channel signaling has unique properties that are easily detectable by ULP wireless receivers consuming only 100 s of uW (micro Watts) or even less. This technique eliminates the need for specialized transmitter hardware or dedicated channel resources for embedded back-channel signal transmission. Instead, carefully sequenced data bit streams generate back-channel messages embedded in standard compliant OFDM packets. This OFDM back-channel communication is feasible in various modulation formats such as pulse position modulation (PPM), pulse phase shift keying (PPSK) or frequency shift keying (FSK) that are easily decodable by heterogeneous, non-WiFi ULP IoT devices. The OFDM back-channel transmission can be enabled on existing legacy WiFi devices (e.g., smartphones, Access Points, etc.) without any hardware modification. This technique makes an ULP OFDM back-channel receiver operable with 1000× lower power consumption than a commercial low power WiFi receiver and 200× lower power than a Bluetooth/IEEE 802.15.4 Zigbee receiver. The OFDM back-channel can be utilized as a ULP paging/wakeup/interrupt channel enabled by already deployed legacy WiFi devices. This back-channel concept can be extended and generalized to other OFDM based communication systems such as the cellular 4G LTE (long-term evolution).
Demodulating an OFDM modulated WiFi signal is a very power demanding task (typically 200 mW) due to stringent RF/analog frontend specifications and sophisticated digital baseband processing. Many power critical WiFi devices consume a significant portion of its standby power just to maintain the WiFi connection constantly listening to WiFi Access Points (APs). Although WiFi signals are ubiquitously available in urban environments (e.g., Google WiFi APs in the city of Mountain View), the majority of ULP IoT devices cannot utilize WiFi connectivity because of their extremely limited power and/or complexity budget. This disclosure will break this barrier to allow heterogeneous ULP IoT devices to interoperate with already existing WiFi infrastructure with minimal power consumption.
This section provides background information related to the present disclosure which is not necessarily prior art.